(+)-Guaiacin is a compound isolated from the bark of Machilus wangchiana Chun. It shows potent in vitro activities against the release of β-glucuronidase in rat polymorphonuclear leukocytes (PMNs) induced by platelet-activating factor (PAF).
Protein tyrosine phosphatases (PTPs) remove phosphate from tyrosine residues of cellular proteins. Reversible phosphorylation catalyzed by the coordinated actions of protein tyrosine kinases and phosphatases is key to the regulation of the signaling events that control cell growth and proliferation, differentiation, and survival or apoptosis, as well as adhesion and motility. RK-682, a bioactive compound originally isolated from the fermentation of Streptomyces sp. 88-682, is an inhibitor of the PTPs. It inhibits the phosphorylation of CD45 and VHR with IC50 values of 54 and 2 μM, respectively, and arrests cell cycle progress at the G1/S transition. It is also reported to inhibit heparanase (IC50 = 17 μM), an endo-β-D-glucuronidase involved in tumor cell invasion and angiogenesis. RK-682 (calcium salt) is a less soluble version of the free acid.
Antileukinate is a synthetic hexapeptide with an acetylated amino terminus and an amidated carboxyl terminus that inhibits the binding of CXC chemokines to the chemokine receptor CXCR2. It inhibits IL-8 binding to neutrophils (Ki = 2.7-13 μM), prevents neutrophil chemotaxis and β-glucuronidase release, and blocks IL-8-induced skin edema in rabbits. At 53 mg/kg, antileukinate has been shown to protect mice against acute pancreatitis and associated lung injury.